Ticket 47421 - memory leaks in set_krb5_creds

Bug Description:  Valgrind shows memory leaks in set_krb5_creds()

Fix description:  krb5_unparse_name() allocates/returns the principle name.
                  But we can call this function twice without freeing the first
                  returned value.

https://fedorahosted.org/389/ticket/47421

Reviewed by: richm(Thanks!)
(cherry picked from commit db124a2711576de2dd0009528d60b2860e815210)
Ticket 47449 - deadlock after adding and deleting entries

Bug Description:  If multiple clients are each doing their own add/delete of the same entries,
                  the server will deadlock very quickly.

Fix Description:  The server was not signaling an error when it failed to lock the parent
                  entry lock.  I've checked add/mod/modrdn functions as well, and they do correctly
                  unlock the cache entry(this includes the old/new superior for modrdn).

https://fedorahosted.org/389/ticket/47449

Reviewed by: richm(Thanks!)
Ticket 47427 - Overflow in nsslapd-disk-monitoring-threshold

Bug Description:  If you directory try and set the threshold to -2,
                  the server allows it, but it should be rejected.

Fix Description:  Use a signed int when parsing the value.

https://fedorahosted.org/389/ticket/47427

Reviewed by: richm(Thanks!)
(cherry picked from commit 0b30980695509347d8f883ac4405fa727041269f)